U.S. patent number 7,290,613 [Application Number 10/966,937] was granted by the patent office on 2007-11-06 for cement compositions comprising aromatic sulfonated polymers and methods of using the same.
This patent grant is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Russell M. Fitzgerald, B. Raghava Reddy, Ashok K. Santra.
United States Patent |
7,290,613 |
Santra , et al. |
November 6, 2007 |
Cement compositions comprising aromatic sulfonated polymers and
methods of using the same
Abstract
A method of servicing a wellbore that penetrates a subterranean
formation includes displacing a cement composition comprising an
aromatic sulfonated polymer into the wellbore and allowing the
cement composition to set. In an embodiment, a transition time of
the cement composition is less than or equal to about 60 minutes,
alternatively less than or equal to about 50 minutes, less than or
equal to about 40 minutes, less than or equal to about 30 minutes,
less than or equal to about 20 minutes, or less than or equal to
about 10 minutes. Thus, the transition time may be short enough to
inhibit a substantial amount of gas migration into the cement
composition before it sets. In yet another embodiment, the cement
composition exhibits a viscosity that increases from a value of 35
Bc (Bearden units) to about 100 Bc in about 10 minutes or less when
the cement composition sets.
Inventors: |
Santra; Ashok K. (Duncan,
OK), Reddy; B. Raghava (Duncan, OK), Fitzgerald; Russell
M. (Waurika, OK) |
Assignee: |
Halliburton Energy Services,
Inc. (Duncan, OK)
|
Family
ID: |
35427227 |
Appl.
No.: |
10/966,937 |
Filed: |
October 15, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060081373 A1 |
Apr 20, 2006 |
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Current U.S.
Class: |
166/294 |
Current CPC
Class: |
C04B
24/163 (20130101); C04B 28/02 (20130101); C09K
8/493 (20130101); C04B 28/02 (20130101); C04B
24/163 (20130101) |
Current International
Class: |
E21B
33/138 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 430 644 |
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Jun 1991 |
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EP |
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1588130 |
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Apr 1981 |
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GB |
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Other References
Paper entitled "Sulfonic Acid, Organic Chemistry", The Columbia
Electronic Encyclopedia, 2003. cited by other .
Halliburton brochure entitled "Diacel LWL Cement
Retarder/Fluid-Loss Additive" dated 1999. cited by other .
Halliburton brochure entitled "GasStop HT Cement Additive" dated
1999. cited by other .
Halliburton brochure entitled "Halad.RTM. -344 Fluid-Loss Additive"
dated 1998. cited by other .
Halliburton brochure entitled "Halad.RTM. -413 Fluid-Loss Additive"
dated 1998. cited by other .
Halliburton brochure entitled "HR.RTM. -5 Cement Additive" dated
1998. cited by other .
Halliburton brochure entitled "HR.RTM. -25 Cement Retarder" dated
1999. cited by other .
Halliburton brochure entitled "MICROSAND Cement Additive" dated
1999. cited by other .
Halliburton brochure entitled "Silicalite Cement Additive" dated
1999. cited by other .
Halliburton brochure entitled "SSA-1 Strength-Stabilizing Agent"
dated 1998. cited by other .
Halliburton brochure entitled "SSA-2 Coarse Silica Flour" dated
1999. cited by other .
Foreign communication from a related counterpart application dated
Dec. 14, 2005. cited by other .
Office Action dated Mar. 21, 2007 (16 pages), U.S. Appl. No.
11/372,001 filed on Mar. 9, 2006. cited by other.
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Primary Examiner: Bates; Zakiya W.
Attorney, Agent or Firm: Roddy; Craig W. Conley Rose,
P.C.
Claims
What is claimed is:
1. A method of cementing a wellbore, comprising: (a) placing a
cement composition comprising a water soluble aromatic sulfonated
polymer into the wellbore, wherein the aromatic sulfonated polymer
consists essentially of: (i) one or more monomers selected from the
group consisting of partially or fully sulfonated polystyrene;
polv(styrene sulfonic acid); a copolymer of styrene and sulfonated
styrene; sulfonated gilsonite; sulfonated lignin; a copolymer
comprising sulfonated styrene, sulfonated alpha-methylstyrene,
allyloxybenzenesulfonic acid or sulfonated vinyl toluene; one or
more compounds having one of chemical Structures A-F: ##STR00003##
where M is H, alkali or alkaline earth metal, or ammonium; and
combinations thereof; and (ii) from 0 to, less than about 10 molar
percent of one or more monomers selected from the group consisting
of maleic anhydride, acrylic acid, 2-acrylamnido-2-methyl-1-propane
sulfonic acid, methally sulfonic acid or combinations thereof; and
(b) allowing the cement composition to set, wherein the cement
composition has a transition time of less than or equal to about 60
minutes.
2. The method of claim 1, wherein the cement composition has a
transition time of less than or equal to about 40 minutes.
3. The method of claim 1, wherein the cement composition has a
transition time of less than or equal to about 20 minutes.
4. The method of claim 1, wherein the cement composition has a
transition time of less than or equal to about 10 minutes.
5. The method of claim 1, wherein the viscosity of the cement
composition increases from about 35 Bc to about 100 Bc in about 10
minutes or less when the cement composition sets.
6. The method of claim 1, wherein the aromatic sulfonated polymer
consists essentially of alkali metal salts of poly(styrene sulfonic
acid).
Description
FIELD OF THE INVENTION
The present invention generally relates to well cementing, and more
particularly to cement compositions comprising aromatic sulfonated
polymers for reducing a transition time of the compositions and
methods of cementing a wellbore using such cement compositions.
BACKGROUND OF THE INVENTION
Zonal isolation refers to the isolation of a subterranean formation
or zone, which serves as a source of a natural resource such as
gas, oil, or water, from other subterranean formations. To achieve
isolation of a subterranean formation, a well bore is typically
drilled down to the subterranean formation while circulating a
drilling fluid through the wellbore. After the drilling is
terminated, a string of pipe, e.g., casing, is run in the wellbore.
Next, primary cementing is typically performed whereby a cement
slurry is placed in the annulus and permitted to set into a hard
mass, thereby attaching the string of pipe to the walls of the
wellbore and sealing the annulus. Subsequent secondary cementing
operations such as squeeze cementing may also be performed.
One problem commonly encountered during the placement of a cement
slurry in a wellbore is unwanted gas migration from the
subterranean zone into and through the cement slurry. Gas migration
is caused by the behavior of the cement slurry during a transition
phase in which the cement slurry changes from a true hydraulic
fluid to a highly viscous mass showing some solid characteristics.
When first placed in the annulus, the cement slurry acts as a true
liquid and thus transmits hydrostatic pressure. However, during the
transition phase, certain events occur that cause the cement slurry
to lose its ability to transmit hydrostatic pressure. One of those
events is the loss of fluid from the slurry to the subterranean
zone. Another event is the development of static gel strength,
i.e., stiffness, in the slurry. As a result, the pressure exerted
on the formation by the cement slurry falls below the pressure of
the gas in the formation such that the gas begins to migrate into
and through the cement slurry. When gas migration begins, the
cement slurry typically has a gel strength of about 100
lb.sub.f/100 ft.sup.2. The gas migration causes flow channels to
form in the cement slurry. Eventually the gel strength of the
cement slurry increases to a value sufficient to resist the
pressure exerted by the gas in the formation against the slurry. At
this point, the cement slurry typically has a gel strength of about
500 lb.sub.f/100 ft.sup.2. The cement slurry then sets into a solid
mass.
Unfortunately, the flow channels formed in the cement during such
gas migration remain in the cement once it has set. Those flow
channels can permit further migration of gas through the cement
even long after the cement is set. Thus, the cement residing in the
annulus may be ineffective at maintaining the isolation of the
adjacent subterranean formation. To overcome this problem, attempts
have been made to design a cement slurry having a shorter
transition time, i.e., the period of time during which gas
migration into the slurry can occur, which is typically the time
ranging from when the gel strength of the slurry is about 100
lb.sub.f/100 ft.sup.2 (pound force per hundred square foot) to when
it is about 500 lb.sub.f/100 ft.sup.2. While cement slurries having
shorter transition times have been developed, those slurries are
typically very expensive to prepare. Further, their transition
times are still longer than desired.
As such, there continues to be a need for improved methods of
eliminating gas migration during well cementing to reduce the risk
of compromising zonal isolation. It is therefore desirable to
develop relatively inexpensive cement compositions having even
shorter transition times.
SUMMARY OF THE INVENTION
A method of servicing a wellbore that penetrates a subterranean
formation includes displacing a cement composition comprising an
aromatic sulfonated polymer into the wellbore and allowing the
cement composition to set. In embodiments, a transition time of the
cement composition is less than or equal to about 60 minutes, less
than or equal to about 50 minutes, less than or equal to about 40
minutes, less than or equal to about 30 minutes, less than or equal
to about 20 minutes, or less than or equal to about 10 min. As
such, the transition time may be short enough to inhibit a
substantial amount of gas migration into the cement composition
before it sets.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plot of thickening time for a cement composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Cement compositions or slurries may include at least one water
soluble aromatic sulfonated polymer for reducing the transition
times of the compositions. As used herein, the transition time of a
cement composition is defined as the period of time after the
composition is placed into a wellbore annulus during which the
pressure exerted on the subterranean formation by the cement
composition is less than the pressure of the gas in the formation
such that gas migration into the composition can occur. The
transition time is typically the time ranging from when the gel
strength of the composition is about 100 lb.sub.f/100 ft to when it
is about 500 lb.sub.f/100 ft.sup.2. Due to the presence of the
aromatic sulfonated polymer in the cement compositions, the
transition times of the compositions are typically less than or
equal to about 60 minutes, alternatively less than or equal to
about 50 minutes, alternatively less than or equal to about 40
minutes, alternatively less than or equal to about 30 minutes,
alternatively less than or equal to about 20 minutes, or
alternatively less than or equal to about 10 minutes. As a result,
a cement composition may be pumped to its desired location in a
wellbore, e.g., the annulus, and allowed to set without being
concerned that gas migration could compromise its ability to seal
an area of the wellbore. That is, there is insufficient time for
the gas to migrate into and through the cement composition and form
flow channels therein. The water soluble aromatic sulfonated
polymer thus serves as a gas migration control additive in the
cement compositions.
As illustrated in the examples below, the cement compositions also
exhibit a relatively constant viscosity for a period of time after
they are initially prepared and while they are being placed in
their intended locations in the wellbore. Eventually, the cement
compositions quickly set such that the viscosity increases to equal
to higher than above 70 Bearden units of Consistency (Bc) from
about 35 Bearden units (Bc) in less than about 60 minutes. In an
embodiment, the viscosity increases to its maximum in less than
about 10 minutes. This sudden jump in viscosity is very desirable
in preventing the gas migration because it indicates the quick
formation of impermeable mass from a gelled state after placement.
This behavior is often referred to as "Right Angle Set" and such
cement compositions are called "Right Angle Set Cement
Compositions." In contrast, the viscosity of conventional cement
compositions typically increases gradually over time to its maximum
value.
Any suitable water soluble aromatic sulfonated polymer known in the
art operable to provide the desired properties described herein may
be employed in the cement compositions. In one embodiment, an
aromatic sulfonated polymer comprises a polymeric backbone having
sulfonated (i.e., salts of sulfonic acid functional groups)
aromatic rings as pendant groups. Examples of such aromatic rings
include phenyl rings, naphthyl, anthracenyl or phenanthrenyl rings.
Examples of suitable aromatic sulfonated polymers include but are
not limited to compounds having one of chemical Structures A-F
where M is H, alkali or alkaline earth metal, or ammonium;
partially or completely sulfonated polystyrenes such as those
having Structure B; poly(styrene sulfonic acid) such as those
having Structure A and its alkali or alkaline earth metal or
ammonium salts where M=H, alkali or alkaline earth metal, or
ammonium; polymers obtained by polymerizing monomers comprising
allyloxybenzenesulfonic acid (structure not shown); copolymers of
styrene and sulfonated styrene such as those having Structure B;
sulfonated gilsonites; sulfonated lignin; copolymers comprising
sulfonated styrene, sulfonated alpha-methylstyrene, sulfonated
vinyl toluene and the like; and combinations thereof. In some
embodiments such aromatic sulfonated polymers may contain small
amounts other comonomers such as maleic anhydride, acrylic acid,
AMPS (2-acrylamido-2-methyl-1-propane sulfonic acid),
methallysulfonic acid, or combinations thereof. Such additional
monomers may be present in less than 10 molar percent of the
monomer content of the aromatic sulfonated polymer. Of these
poly(styrene sulfonic acid) and its alkali metal salts are
preferred. Suitable commercially available water soluble aromatic
sulfonated polymers include VERSA-TL 130, VERSA-TL-501, VERSA-TL
130, VERSA-TL 77, VERSA-TL 70, VERSA-TL 501 from ALCO Chemical, a
division of National Starch and Chemical Company, Chattanooga,
Tenn., SOLTEX SHALE INBIBITOR from Drilling Specialties Company,
The Woodlands, Tex., and BOREMASTER from Setac Chemical
Corporation, Lafayette, La. In an embodiment, water soluble
aromatic sulfonated compounds may contain the sulfonated aromatic
ring as part of the polymer back bone. Such aromatic sulfonated
polymers may comprise a linear polymer containing three kinds of
unit bonds, i.e., an arylene bond, an ether bond, and a sulfone
bond. Examples of such aromatic sulfonated polymers include those
represented by the following Structures C-F. It is not necessary
that all the aromatic rings are sulfonated in the polymers
containing the aromatic rings as part of the polymer back bone. The
degree of sulfonation is such that the whole polymer becomes water
soluble either in the acid form or when converted to an alkali or
alkaline earth metal or ammonium salt. For the purpose of the
present invention, a sulfonated polymer with solubility of greater
than 1% in cement composition at ambient temperature is considered
water soluble.
##STR00001##
##STR00002##
The aromatic sulfonated polymers of the present invention are
compatible with other components commonly used in cement
compositions. The amount of aromatic sulfonated polymer present in
the cement composition may be in a range of from about 0.1% to
about 5%, from about 1.1% to about 2%, or from about 1.2% to about
1.5%, all percentages being by weight of the cement (bwoc).
The cement compositions may further include cement such as
hydraulic cement, which includes calcium, aluminum, silicon,
oxygen, and/or sulfur and which sets and hardens by reaction with
water. Examples of hydraulic cements include but are not limited to
a Portland cement, a pozzolan cement, a gypsum cement, a high
alumina content cement, a silica cement, a high alkalinity cement,
and combinations thereof. The cement may be, for example, a API
Class A, C, G, or H Portland cement. In an embodiment, ultrafine
particle cement (mean particle size equal to less than 5 microns)
may be used. A sufficient amount of water may also be added to the
cement to form a pumpable cementitious slurry. The water may be
fresh water or salt water, e.g., an unsaturated aqueous salt
solution or a saturated aqueous salt solution such as brine or
seawater. The water may be present in the amount of 30% to 150% by
weight of cement preferably in 40% to 110% by weight of cement.
In an embodiment, the cement the cement compositions may also
include a high temperature strength retainment additive such as
silica flour, which is commercially available from Halliburton
Energy Services, Inc. under the tradename of SSA-1. Other high
temperature strength retaining materials include silica materials,
SILICALITE, SSA-2, and MICROSAND available from Halliburton Energy
Services, Inc. Such materials may be used in amounts ranging from
5% to 45% by weight of cement.
In another embodiment, the cement compositions may additionally
include a set retarder to increase the time required for the cement
composition to set and thus provide a sufficient amount of time for
the composition to be properly placed in the wellbore. Examples of
suitable set retarders include, but are not limited to,
lignosulfonate such as HR-5, a synthetic copolymer such as SCR-100,
SCR-500, an organic acid retarder such as HR-25,
carboxymethyhydroxyethyl cellulose, DIACEL LWL all commercially
available from Halliburton Energy Services, Inc., and combinations
thereof. Such retarders or suitable combinations of retarders may
be used in amounts of 0.1% to about 3% by weight of cement
depending on the temperature of application. In an embodiment, an
amount of such retarders is added that is effective to retain
fluidity and pumpability of cement slurries for 2-6 hrs under down
hole conditions.
As deemed appropriate by one skilled in the art, additional
additives may be added to the cement compositions for improving or
changing the properties thereof. Examples of such additives include
but are not limited to fluid loss control agents such as those sold
under the brand HALAD by Halliburton Energy Services, Inc.,
defoamers, light weight additives such as glass or flyash spheres,
fumed silica and Class F flyash, dispersing agents, weighting
agents, foaming surfactants, and formation conditioning agents.
The foregoing cement compositions may be made by combining all of
the components in any order and thoroughly mixing the components in
a manner known to one skilled in the art. In an embodiment, the
aromatic sulfonated polymer is available in an aqueous solution and
is thus combined with the water before it is mixed with the cement
to form a pumpable slurry. In an alternative embodiment, the
aromatic sulfonated polymer is available as solid particles and is
thus combined with the cement before water is introduced to the
cement.
The foregoing cement compositions may be used in various cementing
operations performed in a wellbore. In one embodiment, the cement
compositions may be employed in primary cementing. Primary
cementing first involves drilling a wellbore to a desired depth
such that the wellbore penetrates a subterranean formation while
circulating a drilling fluid through the wellbore. Subsequent to
drilling the wellbore, at least one conduit such as a casing may be
placed in the wellbore while leaving a space known as the annulus
between the wall of the conduit and the wall of the wellbore. The
drilling fluid may then be displaced down through the conduit and
up through the annulus one or more times, for example, twice, to
clean out the hole. A cement composition then may be conveyed
downhole and up through the annulus, thereby displacing the
drilling fluid from the wellbore. As discussed previously, the
transition time of the cement composition is relatively short such
that little or no gas migration into the composition can occur. The
cement composition then quickly sets into an impermeable mass,
forming a cement column that isolates an adjacent portion of the
subterranean formation and provides support to the adjacent
conduit.
In another embodiment, the cement compositions may be employed in a
secondary cementing operation such as squeeze cementing, which is
performed after the primary cementing operation. In squeeze
cementing, a cement composition is forced under pressure into
permeable zones through which fluid can undesirably migrate in the
wellbore. Examples of such permeable zones include fissures,
cracks, fractures, streaks, flow channels, voids, high permeability
streaks, annular voids, or combinations thereof. The permeable
zones may be present in the cement column residing in the annulus,
a wall of the conduit in the wellbore, a microannulus between the
cement column and the subterranean formation, and/or a microannulus
between the cement column and the conduit. The transition time of
the cement composition is relatively short such that the amount of
gas migration into the composition is limited. The cement
composition is allowed to set within the permeable zones, thereby
forming an impermeable mass to plug those zones and prevent fluid
from leaking therethrough.
EXAMPLES
The invention having been generally described, the following
examples are given as particular embodiments of the invention and
to demonstrate the practice and advantages hereof. It is understood
that the examples are given by way of illustration and are not
intended to limit the specification or the claims to follow in any
manner. In the following examples, the cement compositions were
prepared and tested in accordance with procedures described in the
American Petroleum Institute (API) Specification 10A, 23.sup.rd
Edition, April 2002.
Example 1
Three cement compositions or slurries were prepared that contained
different concentrations or types of aromatic sulfonated polymer,
as shown below in Table 1. In particular, two of the cement
compositions contained different concentrations of sulfonated
polystyrene-A, and one contained sulfonated polystyrene-B. The
sulfonated polystyrene-A and sulfonated polystyrene-B had different
molecular weights as shown in Table 3. Sulfonated polystyrenes A, B
and C were obtained ALCO Chemical, a Division of National Starch
and Chemical Company. For each cement composition, the following
components were blended with the aromatic sulfonated polymer: 100%
class H cement, 48.3% water, 40% SSA-1 strength retainment
additive, 45% HR-5 set retarder, and 0.25% HR-25 set retarder, all
percentages being by weight of the cement. The liquid additives
were added with mix water whereas solid additives were dry blended
with cement.
As presented in Table 1 below, the rheology behavior of each slurry
was tested at a temperature of 80.degree. F. and atmospheric
pressure using a FANN 35 viscometer.
Comparative Example 1
The same procedure followed in Example 1 was used to make and test
a control cement composition containing a currently used gas
migration control additive GASSTOP HT made from tannin grafted with
acrylate monomers, which is commercially available from Halliburton
Energy Services, Inc. Table 1 below also shows the results of the
rheology test performed on this control cement composition.
TABLE-US-00001 TABLE 1 Additive GASSTOP Sulfonated Sulfonated
Sulfonated HT Poly- Poly- Poly- (control) styrene-A styrene-A
styrene-B Concentration, 1.1 1.1 0.55 1.1 % bwoc FANN 35 viscometer
readings, centipoise @ 600 rpm 347+ 347+ 347+ 347+ @ 300 rpm 347+
347+ 242 300 @ 200 rpm 324 230 167 192 @ 100 rpm 202 144 89 96 @ 30
rpm 106 77 28 29 @ 6 rpm 24 17 5.6 6.5 @ 3 rpm 13 9 2.7 3.2
Based on the results in Table 1, the cement compositions containing
the aromatic sulfonated polystyrene exhibited rheology behavior
comparable to that of the GASSTOP HT gas migration control
additive.
Example 2
Four cement compositions or slurries were prepared that contained
different amounts or types of aromatic sulfonated polymer, as shown
below in Table 2. In particular, two of the cement compositions
contained different concentrations of sulfonated polystyrene-A, one
contained sulfonated polystyrene-B, and one contained sulfonated
gilsonite such as BORE MASTER from Setac Chemical Corporation,
Lafayette, La.; or SOLTEX from Drilling Specialties Company, The
Woodlands, Tex. For each cement composition, the following
components were blended with the aromatic sulfonated polymer: 100%
class H cement, 48.3% water, 40% SSA-1 strength retainment
additive, 45% HR-5 set retarder, and 0.25% HR-25 set retarder, all
percentages being by weight of the cement. Liquid additives were
added with mix water whereas solid additives were dry blended with
cement.
The thickening time required for each cement composition to achieve
70 Bearden units of consistency (Bc) was determined while
continuously shearing the composition. While maintaining the cement
composition in a static state, the time required for the viscosity
to change from 35 Bc to 100 Bc was also determined. The thickening
time indicates conversion of pumpable fluid state to a non-pumpable
paste. The time lapse between 35 Bc to 100 Bc is also often
considered as a measure of transition time indicating the viscosity
change to form an impermeable solid mass from a gelled state.
Moreover, the transition time required for the cement composition
to change from having a static gel strength of 100 lb.sub.f/100
ft.sup.2 to having a static gel strength of 500 lb.sub.f/100
ft.sup.2 was determined at 300.degree. F. and 10,000 psi using
MINIMACS equipment supplied by Halliburton Energy Services, Inc.
and described in more detail in Example 3.
The results of these thickening time and transition time tests are
shown in Table 2 below. FIG. 1 is a plot of thickening time for the
cement composition comprising 1.1\5 bwoc sulfonated polystyrene-A
at 300.degree. F. and 10,000 psi.
Comparative Example 2
The same procedure followed in Example 2 was used to make and test
a control cement composition containing GASSTOP HT gas migration
control additive. Table 2 below also shows the results of the
rheology test performed on this control cement composition.
TABLE-US-00002 TABLE 2 Time to Concen- Thickening change from
Transition time tration, time to 35 Bc to 100 lb.sub.f/100 ft.sup.2
to Additive % bwoc reach 70 Bc 100 Bc 500 lb.sub.f/100 ft.sup.2
GASSTOP HT 1.1 6 hrs. 9 min. 50-60 min. (control) Sulfonated 1.1 3
hrs. 2 min. 10 min. Polystyrene-A 40 min. Sulfonated 0.55 3 hrs. 2
min. Not Available Polystyrene-A 42 min. Sulfonated 1.1 4 hrs. 5
min. Not Available Polystyrene-B 55 min. Sulfonated 0.5 Not Not 8
min. Gilsonite Available Available
Based on the results depicted in Table 2, the sulfonated
polystyrene-containing compositions and the sulfonated
gilsonite-containing compositions exhibited much shorter times,
required to change viscosity from 35 Bc to 100 Bc, and shorter
transition times than the control cement composition containing a
prior art material. Increasing the amount of sulfonated
polystyrene-A used in the cement compositions did not affect the
thickening time. As such, the polystyrene-A probably did not
significantly affect the thickening time while the GLASSTOP HT
additive probably retarded the thickening time. The sulfonated
polystyrene and sulfonated gilsonite surprisingly had transitions
times as low as 10 minutes and 8 minutes, respectively.
Accordingly, such aromatic sulfonated polymers could serve as
excellent gas migration control additives in cement
compositions.
Example 3
Three cement compositions or slurries were prepared that contained
different types of aromatic sulfonated polymers, as shown below in
Table 3. In particular, the three cement compositions contained
sulfonated polystyrene-A, sulfonated polystyrene-B, and sulfonated
polystyrene-C, respectively. The molecular weights of these
different sulfonated polystyrene materials are also shown in Table
3. For each cement composition, the following components were
blended with 1.1% of the sulfonated polystyrene material: 100%
class H cement, 35% SSA-1 strength retainment additive, 0.45% HR-5
set retarder, 0.25% HR-25 set retarder, and an effective amount of
water to maintain a slurry density of 16.7 pounds per gallon, all
percentages being by weight of the cement. The liquid additives
were added with mix water whereas solid additives were dry blended
with cement.
The transition time required for each cement composition to change
from having a static gel strength of 100 lb.sub.f/1100 ft.sup.2 to
having a static gel strength of 500 lb.sub.f/100 ft.sup.2 was
determined. Further, the time required to reach 100 lb.sub.f/100
ft.sup.2 (referred to as Zero Gel Time) of each cement composition
was determined according to the following procedure using a
"MINIMACS" Instrument at 300.degree. F. and 10,000 psi.
The static gel strength development test requires specialized
equipment, such as the MACS Analyzer or the MINIMACS Analyzer. This
equipment measures the shear resistance of a cement slurry under
downhole temperature and pressure while the cement remains
essentially static. The test is conducted by mixing the slurry and
placing into the specialized testing device. The slurry is then
stirred and heated to BHCT and downhole pressure according to the
same schedule as the thickening time test. After the slurry reaches
the BHCT, stirring is stopped and the slurry is allowed to
essentially remain static. The stirring paddle is rotated at a rate
of about 0.5.degree./min while the shear resistance on the paddle
is measured. The shear resistance is correlated to the SGS (units
are lb/100 ft.sup.2) and a plot of SGS development is made as a
function of time.
Per the above test procedure, the "Zero Gel Time" is defined as the
"time" the slurry takes to reach a static gel strength of 100
lb.sub.f/100 ft.sup.2 once the stirring is stopped and allowed to
remain static. As illustrated in Table 3 below, the cement
compositions containing the sulfonated polystyrene materials
exhibited low transition times of less than or equal to 40
minutes.
TABLE-US-00003 TABLE 3 Molecular Zero Gel Transition Additive
Weight Time (min.) Time (min.) Sulfonated 75,000 50 40
Polystyrene-A Sulfonated 200,000 60 30 Polystyrene-B Sulfonated
1,000,000 40 40 Polystyrene-C
While preferred embodiments of the invention have been shown and
described, modifications thereof can be made by one skilled in the
art without departing from the spirit and teachings of the
invention. The embodiments described herein are exemplary only, and
are not intended to be limiting. Many variations and modifications
of the invention disclosed herein are possible and are within the
scope of the invention. Use of the term "optionally" with respect
to any element of a claim is intended to mean that the subject
element is required, or alternatively, is not required. Both
alternatives are intended to be within the scope of the claim.
Accordingly, the scope of protection is not limited by the
description set out above but is only limited by the claims which
follow, that scope including all equivalents of the subject matter
of the claims. Each and every claim is incorporated into the
specification as an embodiment of the present invention. Thus, the
claims are a further description and are an addition to the
preferred embodiments of the present invention. The discussion of a
reference herein is not an admission that it is prior art to the
present invention, especially any reference that may have a
publication date after the priority date of this application. The
disclosures of all patents, patent applications, and publications
cited herein are hereby incorporated by reference, to the extent
that they provide exemplary, procedural, or other details
supplementary to those set forth herein.
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